An air intake tract for an internal combustion engine may include an air filter housing in an air filter housing (also known as an air cleaner), possibly a throttle body, and possibly intake air pressure, temperature and mass air flow sensors, among other devices. The intake air tract may be equipped to receive vented engine crankcase vapors into the intake air stream so as to prevent their release into the environment. When an internal combustion engine is shutdown, hydrocarbon vapors from fuel, lubricating oil and other hydrocarbon vapor sources may accumulate within the engine air intake duct as airflow to the engine is no longer drawing the hydrocarbon vapors into the engine to be burned. It is desirable to trap these hydrocarbon vapors within the air intake system to prevent their release into the outside environment. Hydrocarbon vapors are known to be a significant contributing component in urban smog and so their control is desirable.
Gasoline, for example, is a highly volatile hydrocarbon fuel that includes components which transition easily from a liquid to vapor phase. Elevated temperatures such as occurring during normal internal combustion engine operation accelerate the liquid to vapor transition. The hydrocarbon vapors, unless treated or captured, may ultimately discharge into the atmosphere. It is known that hydrocarbon vapors are discharged from the engine crankcase during engine operation. When the engine is shutdown, these vapors may continue to be released from the hot engine crankcase and other components, particularly as the engine cools.
The control of hydrocarbon vapors escaping into the environment is regulated by state and federal regulations. Hydrocarbon traps for capturing hydrocarbon vapors are well known. For example, motor vehicles are commonly equipped with hydrocarbon adsorptive emissions canisters connected to the fuel tank for trapping hydrocarbon vapors, particularly as emitted during refueling.
It is known that certain porous materials such as activated carbon are useful for absorption and removal of organic hydrocarbon vapors. It is known hydrocarbon vapors are liquefied within small micro pores of the activated carbon and may be retained by absorption.
Flow-through types of hydrocarbon traps are known. As air flow must pass through restrictions in such flow-through traps, these traps present an undesired restriction to the air flow.
Various types of hydrocarbon traps for capturing hydrocarbon vapors are known in the art. For example, U.S. Pat. No. 5,914,294 discloses a monolithic trap which adsorbs chemical constituents from a gas stream. This is achieved by bringing the gas into direct contact with the activated carbon in the monolith. One disadvantage of this type of extruded or press formed hydrocarbon trap is that the extrusion and binding process results in a relatively brittle trap that may crack or have individual pieces flake off.
Another example is U.S. Published Application 2005/0223894 which discloses an adsorption element for adsorbing gases and vapors from the intake tract of an engine. The adsorption element has free-flow channels in an element having a spacer layer and an adsorption layer. One disadvantage of this type of corrugated trap is that the trap itself introduces a restriction to airflow in the intake tract.
U.S. Published Application 2007/0130896 discloses a flow-though air filter which includes an upstream filter fleece. The filter fleece is adapted to provide a flame-retardant effect to the air filter. A hydrocarbon trap is not disclosed.
U.S. patent application Ser. No. 12/512,389 (unpublished as of this writing) discloses a hydrocarbon adsorption trap configured for installation into an air intake tract.
Internal combustion engines, particularly diesel engines, may backfire into the air intake tract, discharging superheated combustion byproducts and fuel vapors into the air intake tract. Such a backfire event presents a risk that the hydrocarbon adsorption trap (HCA trap) may ignite and at least partially burn.
Therefore, there remains a need in the art for a hydrocarbon adsorption trap that is flare-resistant, rugged, low in cost, and does not present a restriction to air flow in the air intake tract.